1. Field of the Invention
This invention relates to medical articles, and more particularly relates to a lubricious and antithrombogenic composition and method for its application to a medical article.
2. Background of the Invention
Extensive investigations have been undertaken over many years to find material that will be biologically and chemically stable toward body fluids. This area of research has become increasingly important with the development of various objects and articles which may come into contact with blood, such as artificial organs, vascular grafts, probes, cannulas, catheters and the like.
Synthetic plastics have come to the fore as preferred materials for such articles. However, such materials have the major drawback of being thrombogenic. Even such plastics as polytetrafluoroetheylene and the silicone rubbers, which are more compatible with blood than most plastics, still show thrombogenic characteristics.
Often, use of such articles, as for example, probes, cannulas, catheters and the like, include puncture and passage of the article through the skin. Friction between the patient's skin and the plastic surface of the article may cause substantial discomfort to the patient. Further, catheters are often used in conjunction with an introducer device which typically contains a soft rubber one-way check valve through which the catheter must be threaded. When one surface of an article must slide across another surface, friction may develop which can cause damage to the article. In particular, fragile catheter balloons may be damaged by friction during passage through the valve of the introducer. Thus, both antithrombogenicity and lubricity are highly desirable properties for article surfaces to come into contact with blood.
Surfaces may be rendered lubricious by simple application of any common lubricant. Silicone oils are generally recognized to be among the best lubricants available. Application of a silicone lubricant to a surface is known to result in significant reduction in the surface drag upon catheter insertion, facilitate catheter placement, and reduce the force required for catheter retraction. However, a silicone lubricant coated over a heparinized surface in accordance with the prior art masks the heparin and severely compromises its antithrombogenic activity.
Thrombogenicity has conventionally been counteracted by the use of anticoagulants such as heparin. A variety of heparinization procedures have been reported. For example, Solomon et al., in U.S. Pat. No. 4,521,564, discloses a method to convalently bond heparin to a polyurethane substrate. Eriksson et al., in U.S. Pat. No. 4,118,485, coats a plastic surface with a complex of heparin and either an alkylamine salt or a quaternary amine salt and subsequently stabilizes the heparin by crosslinking with a dialdehyde.
Williams et al., in U.S. Pat. No. 4,613,517, reveals a process for ionically bonding heparin to a polymeric surface including the steps of plasma-treating the surface, absorbing a surface active agent onto the plasma-treated surface, reacting the surface active agent with heparin, and crosslinking the heparin with glutaraldehyde.
Substrates rendered blood compatible by coating with a layer of silicone have been disclosed. Durst et al. in Am. J. of Roent., Radium Ther. and Nuclear Med., 120, 904 (1974) reported that, in vitro, siliconized stainless steel guidewires, polytetrafluoroethylene coated guidewires and polyethylene catheters were hypothrombogenic compared to untreated substrates, but, in vivo in dogs, no antithrombogenic effect was observed except with heparin coated substrates.
McGary et al., in U.S. Pat. No. 4,678,660, discloses dipping a polyurethane substrate into a solution of a complex of heparin and tridodecylmethyl ammonium chloride (TDMAC) in polyurethane to form a layer of the complex in polyurethane on the substrate. A lower leach rate of heparin is claimed for the patented product having heparin distributed throughout the polyurethane layer as compared to heparin ionically bonded to TDMAC on the surface of the polyurethane substrate.
U.S. Pat. No. 4,529,614 to Burns discloses coatings of an anticoagulant and a water soluble copolymeric silicone applied to plastic surfaces. The coatings render the surfaces hydrophobic and dissolve in the blood to impart anticoagulant properties to a sample to be analyzed.
Thus, while the prior art has recognized for many years the desirability of rendering substrate surfaces antithrombogenic or lubricious, there are no reports known to the authors of the simultaneous achievement of both effects. The present invention addresses this need.